Handle NULL strings gracefully during constant registration
Handle NULL strings gracefully during constant registration

When libcurl is compiled not using e.g. libz or SSL, then a call to
curl_version_info could return NULL in the corresponding fields of
curl_version_info_data.

Passing such NULL pointers down to REGISTER_NS_STRING_CONSTANT results
in a segfault during php startup, so let's check for this special case
and register a NULL constant in this case.

Signed-off-by: Michael Heimpold <59934addbc17c0fa64a0bf4bb38537fc23439974@heimpold.de>

m6w6/ext-http,m6w6/ext-http,m6w6/ext-http,m6w6/ext-http